Method for the treatment of textiles after washing

ABSTRACT

The invention provides a method for the treatment of textile after washing, using chitosan to reduce the surfactant activities of the residual anionic surfactant on textile after washing and to neutralize the residual base on textile after washing. The chitosan is represented by the formula (I):

BACKGROUND OF INVENTION

[0001] 1. Field of Invention

[0002] The invention relates to a method for the treatment of textiles, and particularly, to a method for the treatment of textiles after washing, which uses chitosan to reduce the surfactant activities of the residual anionic surfactant on textiles after washing and to neutralize the residual base on textiles after washing.

[0003] 2. Related Art

[0004] Surfactants and human life are closely related since petrochemical surfactants have been synthesized. Consequently, in addition safely of use, it has always been our goal to prevent severe environmental pollution.

[0005] For example, almost all the components of common detergents include anionic surfactant, a base and other additives. However, the problem of dissolution often occurs in common detergents, which results in residual detergents on the textile due to insufficient solubility. There is no effective solution to the problem of residual detergents, which is difficult primarily because the detergents contain anionic surfactant, a base and various additives. Especially in recent years, the claim of “ease of rinse” of the concentrated detergents actually results in an increase in the amount of antifoaming agents in the formulas and gives people the false impression that the detergent is completely removed from the textile; this gives rise to the problem of residual detergents. The most important factor in solving the problem is the treatment material must be safer for human health than anionic surfactant and additives, and will not produce environmental pollution.

[0006] The problems of residual detergents in the human body mainly include: (1) residual base: the regulation function of human skin is affected significantly, and the protective function of the skin surface is reduced, which easily results in bacterial infection and entopic dermatitis, as well as inflammation of the skin after long term use; (2) residual anionic surfactant: the issue of safety regarding anionic surfactants is emphasized nowadays—most of them are not proved to be hazardous, but LAS (Linear Alkyl Benzene Sulfonate) has been proved to induce skin protein denaturing, and to be one of the reason for skin diseases such as allergies, saltrheum, Keratodermia Tylodes Palmaris Progressiva, and others.

[0007] In addition, residual detergents adversely affect textiles after washing, especially in relation to the use of textile softeners. Most commonly used textile softeners are cationic type surfactants. When the cationic surfactant is dissolved in water, it is dissociated into cationic, and the aqueous is almost a weak acid. It is stable in acids and inorganic salts, but is unstable with bases. Thus, when textile softeners and anionic surfactants are used together, a precipitate that does not dissociate is formed. Therefore, after washing textiles with detergents containing anionic surfactants, textile softeners containing cationic surfactants are less effective without washing with a sufficient quantity of water.

[0008] Under normal wash conditions, base and anionic surfactants more or less remain on the textile. When a large amount of detergent is added the situation of the detergent residue and incomplete dissolution is more serious. Furthermore, commonly used water is mostly slightly more base (that is, pH value is greater than 7 slightly), thus the instability of the cationic surfactant is increased and the effectiveness of the detergent is decreased.

[0009] As described above, an effective alternative method is to keep textiles in acidic surroundings after washing by using buffer solutions as an enhancer for the cationic surfactant. But there is some doubt regarding the safety of this method. For reasons of human safety and environmental pollution, the selection of enhancer additives is very difficult, resulting in no effective buffer solution being added into the cationic surfactant. Thus, for most textiles in the post wash phase, large excess amounts of the cationic surfactant are used to soften the textile, or the cationic surfactant is used for softening the textile using large amounts of clean water. Although the methods mentioned above can achieve the softening effect as well, most of the cationic surfactants are chemical synthetics and no matter what kind of cationic surfactant is used, and regardless of how safe, to the ability of both the environment and the human body to safely handle this increase is limited. Thus it is an immeasurable contribution to the environment and human body in reducing usage amount.

[0010] To summarize above, residual detergents not only severely affect the health of human skin, but also make the fiber of the textile brittle. The cationic surfactants used in the post wash softening treatment are combined with the anion of the residual detergents and the efficiency of softening phase of the textile wash is significantly reduced.

[0011] Accordingly, it is an issue today how to effectively reduce the surfactant activities of residual anionic surfactant and to neutralize the base of detergents on textiles, but not produce any serious environmental pollution, in order to keep human skin healthy and maintain the activities of the cationic surfactants for treating the textile after washing.

SUMMARY OF THE INVENTION

[0012] It is an object of the invention to provide a method for the treatment of textiles after washing to effectively neutralize the base of residual detergents on the textiles and to reduce the surfactant activities of residual anionic surfactant, but not to produce environmental pollution, in order to keep human skin healthy and maintain the activities of the cationic surfactants for treating textile after washing.

[0013] To accomplish the above objective, in accordance with the method of the invention for the treatment of textile after washing, the use of chitosan is proposed to reduce the surfactant activities of residual anionic surfactant on textiles after washing and to neutralize the residual base on textiles after washing. In the invention, chitosan is dissolved in an acidic liquid to form a chitosan solution, wherein the chitosan solution contains about 0.00001%˜10% by weight of chitosan. The chitosan is represented by the formula (I):

[0014] The chitosan may be obtained by dissolving the chitosan acid salts in water to form chitosan liquor. The chitosan acid salts are represented by the formula (II):

[0015] Where R is selected from at least one of the group consisting of C_(n-1)H_(2n-1)COOH(where n=1˜3), lactic acid, malic acid, citric acid, ascorbic acid, oxalic acid, succinic acid, malonic acid, adipic acid, pyruvic acid, glutaric acid, tartaric acid, asparagic acid, epoxysuccinic acid, monochoroacetic acid, salicylic acid, itaconic acid, pyrrolidone carboxylic acid, glycolic acid, nitric acid, sulfuric acid, hydrochloric acid, and phosphate acid.

[0016] In accordance with one embodiment of the invention, the after wash textile can be immersed into the chitosan liquor such that the chitosan interact with anionic surfactant and base to reduce the surfactant activities of the residual anionic surfactant and to neutralize the base of residual detergents on the textile after washing. In this embodiment, the chitosan liquor contains about 0.00001% to 0.2% by weight of chitosan.

[0017] In accordance with another embodiment of the invention, the chitosan liquor can be sprayed onto the textile after washing such that the chitosan interacts with the anionic surfactant and the base to reduce the surfactant activities of the residual anionic surfactant and to neutralize the base of residual detergents on the textile after washing. In this embodiment, the chitosan liquor contains about 0.01% to 5% by weight of chitosan.

[0018] From the descriptions above, the method of the invention for the treatment of textile after washing further comprises the combination usage of chitosan and a cationic surfactant in order to maintain the softening effect of the cationic surfactant on the textile after washing while reducing the amount of cationic surfactant used. Wherein, the cationic surfactant is selected from at least one of the group consisting of ammonium salts, quaternary ammonium salts, alkyl pyridium salts, and imidazolines. The concentration of the cationic surfactant is 0.001% owf to 10% owf (owf, on weight of fabric) for the softening treatment of the textile after washing. Specifically, one method may be the combination usage of chitosan and a cationic surfactant for treating the textile after washing by using chitosan first, followed by the cationic surfactant; an alternate method would be the combination usage of chitosan and a cationic surfactant for treating the textile after washing by using chitosan and the cationic surfactant at the same time.

[0019] Because the method of the invention for the treatment of textiles after washing can employ the new application of chitosan, the invention employs chitosan to deal with the anionic surfactant and the base of residual detergents on the textile after washing, it can fulfill the requirement of not producing environmental pollution and at the same time it can effectively neutralize bases and reduces the surfactant activities of the anionic surfactant. It is possible to keep human skin healthy and maintain the activities of the cationic surfactants for treating textile after washing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a schematic diagram showing the method for the treatment of textile after washing according to the preferred embodiment of the invention.

[0021]FIG. 2 is a schematic diagram showing the method for the treatment of textile after washing according to another preferred embodiment of the invention.

[0022]FIG. 3a is a diagram showing the changes of pH value in the solution, when the chitosan solution is treated with 0.1N NaOH solution.

[0023]FIG. 3b is a diagram showing the changes of pH value in the solution, when the chitosan solution is treated with 0.1N HCl solution.

[0024]FIG. 4 is a diagram showing the changes of pH value, when the commercial detergent is added with chitosan.

[0025]FIG. 5a is a photograph showing the precipitant formed form the combination of the commercial detergent and the cationic surfactant C.

[0026]FIG. 5b is a photograph showing the case of the commercial detergent added with chitosan, then with the cationic surfactant C.

[0027]FIG. 6 is a diagram showing the changes of pH value in the solution, when 0.1N NaOH solution is used to titrate the commercial softener solutions and the solution containing commercial softener and chitosan liquor.

[0028]FIG. 7a is a diagram showing the changes of softness using softener A with chitosan or with water.

[0029]FIG. 7b is a diagram showing the changes of softness using softener B with chitosan or with water.

[0030]FIG. 7c is a diagram showing the changes of softness using softener C with chitosan or with water.

[0031]FIG. 7d is a diagram showing the changes of softness using softener D with chitosan or with water.

[0032]FIG. 8a is a SEM picture showing the surface of commercial detergent magnified 5000×.

[0033]FIG. 8b is a SEM picture showing the surface of commercial detergent after chitosan coverage, magnified 5000×.

[0034]FIG. 8c is a SEM picture showing the surface of commercial detergent after chitosan coverage, magnified 35×.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] The preferred embodiments of the method of the invention for the treatment of textiles after washing are illustrated with reference to the accompanying drawings. Wherein, the same elements are illustrated with the same reference label.

[0036] Referring to FIG. 1 of the drawings, according to the preferred embodiment of the method 1 of the invention for the treatment of textiles after washing, chitosan 301 is used to reduce the surfactant activities of the residual anionic surfactant 701 and to neutralize base 702 of residual detergents on the textile 50 after washing.

[0037] In the embodiment, between the detergent 70 is added to wash the textile 50 and the textile softener 90 is added to soften the textile 50, chitosan 301 is used to treat the textile 50 for reducing the surfactant activities of anionic surfactant 701 and neutralizing base 702 contained in the residual detergents 70 after washing. Therefore, it may reduce the damage to the human skin health form residual anionic surfactant 701 and base 702. The interaction of residual anionic surfactant 701 and base 702 with the cationic surfactant 901 of the textile softener 90 is reduced, the softening effect of the cationic surfactant 901 to the textile 50, thus, is improved.

[0038] As described above, according to the preferred embodiment of the method 1 of the invention for the treatment of textile after washing, chitosan 301 is dissolved in acidic liquor 20 to form chitosan liquor 30. Wherein, the chitosan liquor 30 contains about 0.00001%˜0.2% by weight of chitosan 301. The molecule of chitosan is represented by the formula (I):

[0039] Then, the textile 50 after washing is immersed into the chitosan liquor 30 such that the chitosan 301 interacts with the residual anionic surfactant 701 and base 702 on the textile 50 to reduce the surfactant activities of the residual anionic surfactant 701 and to neutralize the residual base 702.

[0040] Chitosan 301 is prepared form acylation of chitin extracted mainly from the shell of crustaceans such as shrimps and crabs, mushrooms and a small number of fungi, algae, yeast and other natural materials. Chitosan 301 is soluble in acidic solutions and forms positively charged groups. The advantages of Chitosan 301 include nontoxic, biodegradable, low immunoreactive, highly hygroscopic, and edible properties. Chitosan 301 also adsorbs heavy metals and oils and has a natural antibacterial effect. Therefore Chitosan 301 is now widely applied in the fields of biomedical science, food industry, textile industry, water treatment, agriculture, and the others.

[0041] Chitosan 301 is a polysaccharide commonly seen in organisms. Instead of damaging the environment, the discharge of Chitosan 301 into the environment feeds plankton. In addition, after adsorbing heavy metals and oils, Chitosan 301 will sink to the bottom of the river to form mud and has the effect of cleaning water. In Japan, Chitosan 301 is one of the raw materials of wastewater treatment agents from ancient times. Thus, the use of Chitosan 301 as the treatment additive after washing cannot cause environmental encumbrance, it is good for the improvement of the environmental quality of water and accelerating the decomposition of the organic material adsorbed.

[0042] Referring to FIG. 2 of the drawings, according to another preferred embodiment of the invention, chitosan 301 is obtained from chitosan acid salts 302 dissolved in water 201. The chitosan liquor 30 formed form dissolving chitosan acid salts 302 in water 201 contains about 0.01%˜5% by weight of chitosan 301. The molecule of chitosan acid salt is represented by the formula (II):

[0043] Where R is selected from at least one of the group consisting of C_(n-1)H_(2n-1)COOH(where n=1˜3), lactic acid, malic acid, citric acid, ascorbic acid, oxalic acid, succinic acid, malonic acid, adipic acid, pyruvic acid, glutaric acid, tartaric acid, asparagic acid, epoxysuccinic acid, monochoroacetic acid, salicylic acid, itaconic acid, pyrrolidone carboxylic acid, glycolic acid, nitric acid, sulfuric acid, hydrochloric acid, and phosphate acid.

[0044] After chitosan acid salts 302 is used to form the chitosan liquor 30, the chitosan liquor 30 is sprayed onto the textile 50 after washing such that the chitosan 301 interacts with the residual anionic surfactant 701 and base 702 on the textile 50 to reduce the surfactant activities of residual anionic surfactant 701 and to neutralize residual base 702.

[0045] Furthermore, the textile 50 after washing is treated with chitosan 301, followed by the softening treatment using the textile softener 90. The residual anionic surfactant 701 and base 702 on the textile 50 have been reduced and neutralized. Thus, the cationic surfactant 901 of the textile softener 90 will not lose its effectiveness against the residual anionic surfactant 701 and base 702. Therefore, the embodiment may enhance the softening effect of the cationic surfactant 901. In other words, it is possible to maintain the softening effect on the textile while reducing the amount of the cationic surfactant 901 used.

[0046] As described above, according to the preferred embodiment of the invention, the method for the treatment of textile after washing further comprises the combined usage of chitosan 301 and the cationic surfactant 901 in order to maintain the softening effect of the cationic surfactant on the textile after washing while reducing the amount of the cationic surfactant used.

[0047] In the embodiment, the cationic surfactant 901 is selected from at least one of the group consisting of ammonium salts, quaternary ammonium salts, alkyl pyridium salts, and imidazolines. In the embodiment, ammonium salts include polyamines, polyamides, fatty amines, alkyl ammonium salts (e.g., fatty amide), ethanolamines, and polyethylene amines; quaternary ammonium salts include alkyl quaternary ammonium salts, dialkyl quaternary ammonium salts, fatty ammonium salts, dimethyl dialkyl quaternary ammonium salts, and diamide quaternary ammonium complex; and imidazolines include alkyl amide imidazoline combination. The concentration of the cationic surfactant 901 is 0.001% owf to 10% owf for the softening treatment of the textile after washing. The method of the combined usage of chitosan 301 and a cationic surfactant 901 will be illustrated in detail hereinafter. At first chitosan 301 is used to treat the textile 50 after washing, then the cationic surfactant 901 is used to treat the textile 50 after washing. Alternatively, the method of using chitosan 301 and the cationic surfactant 901 at the same time may be used for treating the textile 50 after washing.

[0048] Generally, the cationic surfactant 901 is a chemically synthesized material, mainly consisting of primary, second, and ternary ammonium salts, quaternary ammonium salts, alkyl pyridium salts, imidazolines and pyridium salts. The dissociated cationic surfactant 901 in aqueous solution is exhibited cationic. The property of the cationic surfactant is just opposite to that of anionic surfactant 701. Thus, it is called “reverse soap”. The solution of the cationic surfactant is almost a weak acid. It is stable with acids and inorganic salts, but it is unstable with alkalis. If the cationic surfactant 901 interacts with the fiber that is anionic in water, it will discharge and agglutinate. The cationic surfactant will be adsorbed on the fiber to attain the effect of softening textiles. However, it has no effect in decomposing and removing greasy dirt. It is rarely used as a detergent. The cationic surfactant 901 generally has an antibacterial effect and strong interface absorbability, thus it is widely used as wetting agents, leveling agents, softener, antistatic agents, fixing agents etc.

[0049] The softening treatment is the adjustment of friction resistance between fibers themselves or between fibers and body to give the textile a soft and smooth touch. It is important in the softening effect that the static friction coefficient is lowered. Generally, the ability to lower the static friction coefficient is cationic>polyester type nonionic>polyethylene glycol type nonionic>mineral oil. The lubricative effect of surfactant is limited by moistening ability. When the surface is moist, the adsorption is improved and the lubrication is more complete. Take the cationic surfactant, which is the best in lowering the static friction coefficient but is a poor cleaner. It is however good in moisturizing, permeability, emulsion, and dispersibility. Therefore it is the best choice for textile softening treatment. In particularly, the quaternary ammonium salts having many active groups and function as a bactericide and are applied in many fields in the real world.

[0050] In the invention, its ability to adjust pH levels primarily comes from the characteristic of structure of the chitosan used, as shown in formula (I). In acidic circumstances, the amino group of chitosan is positively charged. By the force of hydrogen bonding, the whole molecular chain is extended and soluble in water. When the amount of H+increases, the structure of chitosan is extended further, the winding interior amino groups is exposed to adsorb the excess H+ such that the pH value is not lowered acutely. On the contrary, chitosan quickly releases its hydrogen ion to neutralize the alkali as it meets an alkaline group. If the electricity of chitosan is insufficient, chitosan will be deposited onto the surface of the alkali in the form of formula (I). In addition, the speed of deposition as chitosan meets the alkali is much faster than the speed of dissolution as chitosan is in acidic solution, thus all chitosan is deposited onto the surface of the alkaline material to attain the covering effect before alkaline material is completely neutralized. For the reasons described above chitosan functions to keep the pH value from changing too acutely and maintain the solution in the desired acidic circumstance, whether it is in acidic or alkaline circumstance. Take the fibrous products that frequently contact with body as an example, it is possible to employ the function of adjustment described above to neutralize the residual acid or alkali of chemicals, to control the pH range of the surface of the fibrous products suitable for skin by way of rinse, immersion, spray, or coating, and to obtain the most comfortable feeling upon touching or wearing.

[0051] From the view of safety, chitosan is one of the raw materials used in producing artificial skin. It has been proved by experiments that high purity chitosan will not induce cell-toxicity. Further, because the positively charged amino groups have a puncturing effect on bacteria, the surface of the material treated with chitosan has some anti-bacterial effect. Therefore, chitosan is widely applied in deodorization and anti-bacterium of fiber nowadays. It is also the safest anti-bacterium material. The development of this class of products is most active in Japan, such as in JP09291478; both chitosan and quaternary ammonium salts are combined onto the polyester fiber by way of chemical reactions to perform an anti-bacterial treatment. It utilizes the anti-bacterial property of chitosan and quaternary ammonium salt to make the fiber superior in anti-bacterial property and it utilizes chemical bonding to make the fiber resistant to water. The principle is to take advantage of the safeness of chitosan to reduce the contact between the more toxic quaternary ammonium salt and human body, which increases the safety of the fiber. From the research described above, the residual chitosan of the invention is safe, even the peripheral areas of the residues may have small amount of the anti-bacterial ability. Therefore, the textile treated by chitosan is suitable for contact with the skin.

[0052] Chitosan itself is a polymer of polysaccharide. It has the effect of forming film while drying. Thus, in its physical properties, after the textile treated by chitosan has been dried, chitosan can not only protect the fiber, but also allow the branched fiber to be joined, and reduce the friction between fibers with each other. Since the forming film is highly hydrophilic and highly hygroscopic, the fiber with the film is reduced in the static caused by friction between fibers and is thus reduced the entanglement and adhesion between fibers.

[0053] Furthermore, chitosan itself is highly hygroscopic, and the amino group may bear a positive charge, thus the adhesive ability to fibers is good. The principle is similar to the application of cationic surfactants as textile softener. However, the polysaccharides in its chemical properties are less lubricative than long-chain alkanes. Compared with commercialized products, it is relatively poor in the softening effect. But in fact chitosan has some lubricative effect, if concerned about its physical properties, safety, and environment improvement, chitosan is still the better choice.

[0054] Moreover, chitosan is soluble in formic acid, acetic acid, propionic acid, lactic acid, malic acid, citric acid, ascorbic acid, oxalic acid, succinic acid, malonic acid, adipic acid, pyruvic acid, glutamic acid, tartaric acid, asparagic acid, nitric acid, hydrochloric acid, phosphoric acid and other acids. The acid salts can be prepared by spray drying. When chitosan is dissolved in acidic liquor, it can form a viscous polymer solution because of its polymer property of a polysaccharide. The viscous property can provide a good physical dispersion, and it is positively charged in acidic environment, thus it can be applied in the solution required of positively charged environment for use as an electrical gel suspension, and to stabilize the whole solution. The principle and properties are utilized in U.S. Pat. Nos. 5,126,392 1 and 5,447,643.

[0055] Therefore, in the preferred embodiment of the invention of the method for the treatment of textile after washing, chitosan liquor 30 can be prepared by dissolving chitosan acid salts 302 in water.

[0056] To summarize the above, when chitosan and a typical cationic softener are used together, the softening effect of chitosan is improved, and the cationic surfactant is kept in a weak acidic environment to attain the best-charged effect. Under moderate formulation, the solution will not be acidic enough to corrode the skin. Particularly, when the cationic surfactant is used as softener in families, the inevitable residual soap bases from laundering elevate the pH and reduce the amount of cationic ions. Therefore it is usually necessary to increase the amount of the cationic surfactant used, rinse, or increase the acidity (or, lower the pH value) as required. The addition of chitosan provides the forth option and controls whiten the suitable pH value. Moreover, chitosan itself has some lubricative effect to replace the cationic surfactant. For the both reasons described above, it is possible to substantially reduce the amount of cationic surfactant used to achieve the goal of reducing the waste of the environment.

[0057] From the following seven examples, the concrete effects of the invention are described. Wherein, the commercialized cationic surfactants before processing are in the form of solid or liquid. Generally, the solid content of the cationic surfactant in liquid is between 5 and 15%. But after processing into commercialized textile softener, the solid content is only between 2 and 10%. To evaluate the precise properties of commercial products, as to liquid cationic surfactants, the experiments are conducted by the weight of liquid, but when the component amount is calculated, it should be on the basis of solid amount. In the present experiment, two commercial textile softeners A and B, and two raw materials of cationic softener C (fatty ammonium salt—solid) and D (polyamine—liquid) are tested.

EXPERIMENT EXAMPLE 1

[0058] The changes of chitosan in acidic and basic environments are shown in FIGS. 3a and 3 b. From the experimental data of FIGS. 3a and 3 b, wherever in acidic or basic environments, chitosan solution can prevent the pH value from gradually going up or down. Thus it is possible to choose either a higher or a lower pH value for the chitosan solution treatment of the textile according to the different textiles used and to adjust the suitable pH range for human comfort.

EXPERIMENT EXAMPLE 2

[0059]FIG. 4 shows the changes of pH value after 5% chitosan solution is added respectively in 2L water dissolving 0.1 g of A detergent, 2L water dissolving 0.2 g of A detergent, and 2L water. This experiment is conducted by stirring 5 min and then testing the pH value to simulate the case of chitosan adjustment after the base of the detergent remains. The result shows that even if a little amount of chitosan is added, it is effective in neutralizing the basicity of water and lowering the pH value.

EXPERIMENT EXAMPLE 3

[0060]FIGS. 5a and 5 b show the reduction of surfactant activities of the anionic surfactant due to chitosan. In FIG. 5a, 5 g of A detergent is dissolved in 12 L water. 1 g of 9% C cationic surfactant is added directly into 150g of the above detergent solution. After standing 20 min, the precipitants happen. C cationic surfactant is combined with anionic surfactants in water to form cloudy precipitants. In FIG. 5b, 4 g chitosan solution containing 5% chitosan and 2% acetic acid is first added into 150 g of same detergent solution, and then 1 g of 9% C cationic surfactant is added. After standing 20 min, it is found that the addition of chitosan does effectively reduce the surfactant activities of the anionic surfactant and thus reduce the combination with the cationic surfactant. From the result of experiments, the more chitosan added, the better the effect of reducing the surfactant activities of the anionic surfactant and the less precipitant happen.

EXPERIMENT EXAMPLE 4

[0061] When 50 g of commercial softener is neutralized with 0.1N NaOH, the changes of the pH values with or without addition of chitosan are shown in FIG. 6. From the experimental data of the FIG. 6, all the pH values of the commercial textile softeners A, B, C, and D are rapidly increased in basic environment, and the viscosity is thus increased. Since the major components of the softener all are positively charged cationic surfactants, the pH value may seriously affect the amount of charges and may further affect its function. From the figure, it also shows some brands prepare the softener with a lower pH value. Although an acidic environment is good for increasing the amount of charges in the cationic surfactants, it is not good for human skin. And it has no resistance to the environment, that is, it has no effect of practical adjusting environment. If excess acid is added without neutralization, it harms both the human body and the textile. After sample C is added with chitosan (E), the experiment is conducted in the same way. The result obviously shows the pH gradually increases as the basicity increases, and all the pH are kept within the range suitable for human body. Therefore it is possible to greatly increase the stability of cationic surfactants used, and to keep the environmental pH within the range of safety. This proved that the addition of chitosan indeed effectively controls the change of pH value.

EXPERIMENT EXAMPLE 5

[0062] From FIGS. 7a to 7 d, 4 g of sample respectively added into 2L water, a nylon that has been processed through ordinary washing procedures is disposed. After stirring for 5 min, it is cut into 250 mm×20 mm and tested the change in its softness after A, B, C, and D is respectively diluted in S (5% chitosan & 2% CH3COOH in water) and W (water), according to CNS 13752, L3243 (JIS 1018) Heart Loop method (the length is in proportion to the softness). The overlapping part of the figure can be considered the excess amount of the cationic surfactants used, and the bending point of the dilution curve can be considered the minimum effective concentration for maximum softness. The bigger the area under the curve represents the better the softening effect of the softener. From the experiments, both the chitosan solution and the cationic surfactants are positively charged acid, and the combination has good effect. If added separately and sequentially into water, the result is-same. From the result of the experiment, for example, the minimum effective concentration for maximum softness is 2.75 g for oftener B, but only 2.5 g in combined with chitosan is needed to attain the same softening effect. In other words, it is possible to reduce 10% amount of cationic surfactant added. At low concentrations, the addition of chitosan improves the softening effect more obviously.

EXPERIMENT EXAMPLE 6

[0063] Experiment example 6 shows the affect of detergents to softness. The experiment is conducted with minimum effective concentration of softener C. The detergent is added into 2L water to stir and dissolved. 4 g of softener sample and nylon are added and stir 5 min. The change of the softness is measured. The result is shown in the following table: Addition Addition Addition No deter- of 0.1 g of 0.2 g of 0.3 g gent added detergent detergent detergent (mm) A (mm) A (mm) A (mm) E 76.85 75.63 75.03 74.58 C/(C + W) = 68.75% F 76.88 76.00 75.28 74.70 C/(C + W) = 68.75%

[0064] Wherein, S represents the solution containing 5% chitosan & 2% CH3COOH, and W represents water. In the experiment, the presence of the detergent does reduce the effect of the cationic surfactant, and the addition of chitosan does inhibit the negative effect and keep the whole solution in a more stable and effective state. But if the amount of detergent is excessive, the chitosan is completely consumed and cannot keep the state.

EXPERIMENT EXAMPLE 7

[0065] The detergent was put into the solution containing 5% chitosan and 1% acetic acid. After precipitating, it was filtered and washed with distilled water, and then air-dried. Thus was obtained a sample after coverage. The original detergent and the sample after coverage are observed under scanning electronic microscopy (SEM), as shown in FIGS. 8a to 8 c. FIGS. 8a and 8 b is the 5000-fold magnified SEM photograph of the surface structure observed. FIG. 8c is the 35-fold magnified SEM photograph of the structure of the sample after coverage observed. From the experimental results, Since detergent contains lot of base and anionic surfactant, chitosan releases hydrogen ion form formula (I) to neutralize the base and forms precipitates deposited on the surface of the detergent, which results in a covering film surrounding the detergent particle. From the cross-sectional view of FIG. 8c, the structure of the covering film of chitosan obviously covers the detergent completely.

[0066] According to the preferred embodiment of the invention of the method for the treatment of textile after washing, the effect of chitosan used will become apparent from the experimental example described above.

[0067] One skilled in the art could carry out various equivalent modifications of the embodiment of the invention without departing from the spirit and scope of the invention.

[0068] For examples, one skilled in the art could dissolve chitosan 301 in acidic liquor 20, and the resulting chitosan liquor 30 contains about 0.01% to 5% by weight of chitosan 301. Then, the chitosan liquor 30 can be sprayed onto the textile 50 after washing such that the chitosan 301 interacts with anionic surfactant 701 and base 702 to reduce the surfactant activities of residual anionic surfactant 701 and to neutralize base 702 of residual detergents on the textile after washing.

[0069] And for another examples, one skilled in the art could dissolve chitosan acid salts 302 in water to form the chitosan liquor 30 containing about 0.00001% to 0.2% by weight of chitosan 301. Then, the textile 50 after washing can be immersed into the chitosan liquor such that the chitosan 301 interact with anionic surfactant 701 and base 702 to reduce the surfactant activities of residual anionic surfactant 701 and to neutralize base 702 of residual detergents on the textile after washing.

[0070] Therefore, all described above are only illustrative and not restrictive. All equivalent changes and modifications without departing form the spirit and scope of the present invention should be included in the appended claim. 

What is claimed is:
 1. A method for the treatment of textiles after washing, which uses chitosan to reduce surfactant activities of residual anionic surfactant on textile after washing and to neutralize residual base on the textile.
 2. The method of claim 1, wherein the chitosan is dissolved in an acidic liquor to form chitosan liquor, the chitosan liquor contains about 0.00001%˜10% by weight of chitosan, and the chitosan is represented by the formula (I).


3. The method of claim 1, wherein the chitosan is prepared by dissolving the chitosan acid salts in water to form a chitosan liquor, the chitosan liquor contains about 0.00001%˜10% by weight of chitosan, and the chitosan acid salts are represented by the formula (II):

wherein R is selected from at least one of the group consisting of C_(n-1)H_(2n-1)COOH(where n=1˜3), lactic acid, malic acid, citric acid, ascorbic acid, oxalic acid, succinic acid, malonic acid, adipic acid, pyruvic acid, glutaric acid, tartaric acid, asparagic acid, epoxysuccinic acid, monochoroacetic acid, salicylic acid, itaconic acid, pyrrolidone carboxylic acid, glycolic acid, nitric acid, sulfuric acid, hydrochloric acid, and phosphate acid.
 4. The method of claim 1, wherein the textile is immersed into a chitosan liquor formed from the chitosan to reduce the surfactant activities of the anionic surfactant and to neutralize the residual base, the chitosan liquor contains about 0.00001% to 0.2% by weight of chitosan.
 5. The method of claim 1, wherein chitosan liquor formed from chitosan is sprayed onto the textile to reduce the surfactant activities of the anionic surfactant and to neutralize the residual base, the chitosan liquor contains about 0.01% to 5% by weight of the chitosan.
 6. The method of claim 1, which further comprises of: using the chitosan and a cationic surfactant, together, to keep the softening effect of the cationic surfactant on the textile after washing while reducing the amount of the cationic surfactant used.
 7. The method of claim 6, wherein the cationic surfactant is selected from at least one of the group consisting of ammonium salts, quaternary ammonium salts, alkyl pyridium salts, and imidazolines, and the concentration of the cationic surfactant is 0.001% owf to 10% owf (owf, on weight of fabric) for the softening treatment of the textile after washing.
 8. The method of claim 6, which is treating the textile after washing by chitosan first, followed by the cationic surfactant.
 9. The method of claim 6, which is treating the textile after washing by chitosan and the cationic surfactant at the same time. 